Light emitting diode (LED) lighting systems are becoming more prevalent as replacements for existing lighting systems. LEDs are an example of solid state lighting (SSL) and have advantages over traditional lighting solutions such as incandescent and fluorescent lighting because they use less energy, are more durable, operate longer, can be combined in multi-color arrays that can be controlled to deliver virtually any color light, and generally contain no lead or mercury. In many applications, one or more LED dies (or chips) are mounted within an LED package or on an LED module, which may make up part of a lighting unit, lamp, “light fixture” or more simply a “fixture,” which includes one or more power supplies to power the LEDs. An LED fixture may be made with a form factor that allows it to replace a standard fixture or bulb. LEDs can also be used in place of florescent lights as backlights for displays.
For most LED lamps and fixtures, LEDs may be selected to provide various light colors to combine to produce light output with a high color rendering index (CRI). The desired color mixing may be achieved, for example, using blue, green, amber, red and/or red-orange LED chips. One or more of the chips may be in a package with a phosphor or may otherwise have a locally applied phosphor. For example a red LED may be combined with a blue LED and a yellow phosphor to provide a blue-shifted-yellow plus red color system. Translucent or transparent materials may be used with LED lighting fixtures to provide diffusion, color mixing, to otherwise direct the light, or to serve as an enclosure to protect the LEDs.
Rigid or semi-rigid materials may be included in a fixture or lamp as optical elements external to the LED modules themselves. Such optical elements may allow for localized mixing of colors, collimate light, and provide the minimum beam angle possible. Such optical elements may include reflectors, lenses, and/or lens plates. Reflectors can be, for example, of the metallic, mirrored type, in which light reflects from opaque silvered surfaces, or be made of or use white or near-white highly reflective material, or diffusive material. Reflectors can also made of or include a substrate made of plastic or metal coated with another material. Lenses can vary in complexity and level of optical effect, and can be or include traditional lenses, total internal reflection optics, or glass or plastic plates with or without coatings or additives.